This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines may combust a mixture of air and fuel in cylinders and thereby produce drive torque. Air and fuel flow into and out of the cylinders may be controlled by a valvetrain. The valvetrain may include a camshaft that actuates intake and exhaust valves and thereby controls the timing and amount of air and fuel entering the cylinders and exhaust gases leaving the cylinders. In a condition in which fuel is no longer being provided to the engine, e.g., during deceleration (such as braking) to reduce fuel consumption, during operation from electric power in a hybrid vehicle or during cylinder deactivation, the engine's pistons may still pump within the cylinders. This is sometimes referred to as “fuel cutoff” or as the “fuel cutoff condition”. This pumping without associated combustion may create a pressure differential between the crankcase and combustion chamber, which may lead to oil being pulled from the crankcase into the combustion chamber, intake manifold and/or exhaust manifold. This oil pullover may result in increased oil residue and contamination on the pistons, intake and exhaust manifolds, fuel injectors and valves, as well as increased emissions and poor oil economy.